SPOILERS BELOW
She knew that was a low blow, but she was using people's/society's prejudice against them in order to steal the medicine she was looking for
Besides that, the writers knew that her character would get a pass because she's in a relationship with a black man. That stunt may not have gone over well with viewers if Trish did it; even with the same intent as Jessica.
As for Luke, the married woman plot point showed three things:
a) Luke is noble. He broke it off immediately when he found out she was married.
b) Jessica has been into Luke for a while, and moved to eliminate the competition
c) A plot device for Luke to demonstrate his powers when the husband's friends attacked him at the bar.
At the end of the day art is subjective and we all have our own opinions. You are not "wrong" for not liking it, and those of us who liked it are not "wrong", either. I enjoyed the series very much and can't wait for the Luke Cage series.